Blackout in a Narrow Channel with Emergency Generator Breaker Failure
At 02:15, while the container ship is transiting a narrow channel at 8 knots, the 6.6 kV bus suffers a blackout. The sequence was: No. 3 diesel generator tripped on overcurrent as the bow thruster started; bus frequency fell to 57 Hz; No. 1 and No. 4 generators tripped on underfrequency; the main engine stopped on low lube oil pressure. The emergency generator started and is running, but its breaker has not closed, so the emergency switchboard is dead. Steering is on the emergency hydraulic pump, but the rudder indicator is sluggish. The bridge reports the ship is drifting towards the channel edge. The engineer on watch has one greaser and one electrician available.
1. What immediate actions would you take to restore essential power and steering?
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First confirm the emergency generator is actually running at correct voltage and frequency. Check the breaker control selector, control supply, undervoltage relay and closing spring. If the automatic close has failed and the generator is healthy, close the breaker manually in accordance with the local procedure and confirm the emergency switchboard is energised.
Start the emergency steering pump and confirm rudder response. Tell the bridge to steer using the emergency system, reduce speed or stop the main engine, and be ready to use hand steering or anchor if the channel edge is close.
Check for fire, flooding or smoke in the engine room before energising more circuits. Muster the available crew, call the chief engineer and electrician, and keep the bridge informed of progress.
Do not attempt to restart the main engine until lube oil and cooling water are available. The immediate priority is control of the ship, not restoration of all power.
2. Describe the sequence for restoring main power and the main engine. Why does the order matter?
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Confirm all main generator breakers are open and the main bus is dead. Start one main generator locally or from the emergency board, bring it to rated voltage and frequency, and check the bus for faults. Close the generator breaker to the main bus and confirm the emergency tie or interlock is correct.
Reset the preferential trips and start essential auxiliaries in sequence: lube oil pumps, cooling water pumps, fuel booster and supply, control air, boiler and steering gear. Monitor frequency and current after each step; do not start large loads together.
Only then start the main engine, first on air and then on fuel, and confirm lube oil pressure, cooling water flow and steering before increasing load.
The order matters because generators and the bus cannot absorb all loads at once, and the main engine will trip or be damaged without lubrication and cooling. Sequential restoration also prevents a second blackout caused by overload.
3. What records, alarms and investigations should follow the blackout?
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Record the time, sequence of trips, generator loads before the event, bus frequency, bow thruster start command, main engine stop and restoration times in the engine log and bell book. Preserve the alarm and event log before it is overwritten.
Investigate the No. 3 generator overcurrent trip, the underfrequency protection settings and the bow thruster starting load. Check whether the generator protection coordinated with the thruster starting demand, and whether the bus frequency decay was due to governor response or load shedding failure.
Investigate why the emergency generator breaker did not close automatically: undervoltage relay, breaker mechanism, control supply, auto/manual selector or battery. Test the automatic start and breaker close.
Report to the company and, where required, to class or flag. Conduct a blackout drill and review the load-shedding and preferential trip schedule with the electrical officer.